CFD investigation of the effect of spinneret geometry on the flow behavior of multiphase polymeric fluids
Ünal, Dilay (2014) CFD investigation of the effect of spinneret geometry on the flow behavior of multiphase polymeric fluids. [Thesis]
Nano or micro particle integrated polymeric fibers are commonly produced via so-called wet spinning process. During the process, particle containing polymer solution is exposed to high shear stresses while passing through the spinneret holes, and high shear stresses give rise to increased viscosity (shear thickening). In the present work, it was aimed to investigate parameters that affect the flow behavior of shear thickening fluids. The fluid considered in the simulations was prepared by dispersing silica nanoparticles in poly(ethyleneglycol), and the resulting fluid was a complex fluid which shows shear thinning until a certain shear rate, and above that shear rate it shows shear thickening. The effects of various parameters on the flow properties of the fluid have been investigated over a wide range of conditions. The variables studied are: geometry (reservoir depth, channel length, contraction width, edge roundness), velocity (0.02-0.12 m/s). A two-dimensional simulation model based on an Eulerian-Eulerian multiphase approach is considered to simulate particle containing polymeric fluid. The governing equations and constitutive relations for both phases are solved using the finite volume method, by employing the FLUENT software of ANSYS Workbench. Since it would be computationally too expensive to model the entire spinneret, only one single hole was considered as the computational domain. It was found that reservoir depth and channel length have slight effect on the viscosity but at the same time contraction width and roundness of the edge of the contraction has a significant effect on the viscosity profile. Besides, by increasing velocity fluid viscosity increased as well.
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